1. Field of the Invention
This invention relates generally to pavement construction and particularly to an improved construction for underground utility access assemblies. More specifically, the invention includes an improved construction for raising the manhole ring and cover to proper elevation, and a process and tool for producing the improved construction.
2. Related Art
Subterranean utility lines have been employed for many decades and have typically been laid adjacent to or beneath roadways. The need for access to utilities has necessitated the addition of access holes at various points along a utility line. These access holes are commonly called "manholes" and are covered with what is generally known as "manhole covers".
Manhole covers are generally comprised of cast iron, are circular in configuration, and have a suitable diameter for a particular utility or road construction project, typically, but not restricted to, 12-48 inches. In usage, the top surface of a manhole cover is generally flush with the pavement or road surface, so as to not generate a depression in the road, which would otherwise tend to be the source of a myriad of problems. On such problem would be the unnecessary bumps for traveling vehicles. Another such problem would be the creation of locations where water may accumulate and, by the expansive forces created by its freezing, cause discontinuity between the manhole ring and the surrounding pavement. Such discontinuities would then perpetuate a destructive process by admitting more water into the surrounding area, which could then aggravate the problem by similar subsequent freezing and thawing action. Therefore, a general requirement for both new road construction and reconstruction is that manhole covers be generally flush with the pavement surface.
In the case of new road construction, current practice is to supply a pre-cast concrete manhole cone 10, also called a "cone section", which is put in place in an excavated hole over the buried utility line at the job site. These concrete manhole cones extend upward from the buried utility line to usually less than 2 feet below the road surface. This distance between the cone and the road surface allows for installing the manhole ring (onto which the manhole cover is located in its final assembled position) in such fashion as to provide a flush fit between the manhole cover and the road surface. The distance between cone and road surface is greater than the height of the manhole ring, so that there is a void space between the top of the concrete cone section and the bottom of the manhole ring. In conventional practice, this space is typically filled with bricks, mortar, cement block, or pre-cast concrete circular grade rings 14 of different thickness grouted in place. After the manhole ring is raised above the cone by these bricks or grade rings to the proper elevation and orientation, concrete 20 is poured around the bricks or grade rings and the manhole ring to form a sealed system extending from the cone to the manhole ring. Because the manhole ring is initially buried with the cone beneath the fresh pavement, and then uncovered and raised into correct position by the grade ring technique, the process of lifting and positioning the manhole ring is called "raising".
In the construction of such prior art systems, difficulty is encountered in the raising process, particularly at the stage where it is desired to make the surface of the manhole ring and cover flush with the final road surface. The difficulty in matching the paved surface is of special concern for construction of new road surfaces. Currently, as discussed above, the pre-cast concrete grade rings are available in varying thickness to allow for custom adjustment as each individual case requires, and these rings are set in grout to obtain the final required height adjustment. Still, the adjustment of a manhole ring location by this technique tends to be inaccurate and time-consuming. Also, the pre-cast grade rings are costly and cumbersome to use.
It is an object of the present invention, therefore, to alleviate the necessity to use pre-cast concrete grade rings, bricks, or blocks in these constructions. It is a further object of the present invention to reduce the overall cost and difficulty of construction of utility line access systems.